Embodiments of the present invention relate to an oil transfer assembly for supplying oil into a moving, rotating tube. In particular, the present description refers explicitly to a tube that transfers oil to the nose cone of a propeller driven by a planetary gearbox, without loss of generality as a result.
In aeronautical turbo-propeller engines, it is known how to provide a planetary gearbox to operate a drive shaft that supports the propeller and makes it rotate. In general, the nose cone of the propeller has inside it a hydraulic actuator which is controlled in such a way as to vary the pitch of the propeller blades and is supplied with oil through a tube, normally called a beta tube. This tube extends along the axis of the propeller and the drive shaft and has an intermediate section supported inside the nose cone of the propeller and an axial end housed in the drive shaft. When in use, this tube rotates together with the propeller and translates axially upon activation of the hydraulic actuator.
The need has been felt for supplying oil in this tube to the hydraulic actuator, without providing radial holes through the drive shaft. It is also appropriate to provide for such arrangements so as to compensate for the imperfect alignment between the axial ends of the tube, due to inevitable assembly tolerances and processing and to the distortions due to the operating loads.